Conventionally, an electric motor provided with a speed reduction mechanism is used in many cases as a driving source for a sunroof apparatus, etc. Such an electric motor used in the sunroof apparatus, etc., includes: a yoke in which an armature spindle (rotating shaft) is rotatably housed; and a gear case (casing) which is connected to an open end of the yoke and in which a speed reduction mechanism for reducing the rotation speed of the armature spindle is housed. A mechanism including: a worm which is rotated by the armature spindle; and a worm wheel having gear teeth which is engaged with the worm are used as the speed reduction mechanism, thereby producing a relatively large power in spite of its compact structure.
Additionally, when opening and closing a sunroof which is an openable and closable element, it is necessary for the electric motor used in the sunroof apparatus, etc., to detect the opening and closing movement of the sunroof, and to control the rotation of the armature spindle. Therefore, a control board (circuit board) is provided so as to meet this requirement. The control board, together with the speed reduction mechanism, is housed in the gear case, and is protected from being exposed to rainwater, dust, etc. Furthermore, a gear cover (cover member) is provided between the speed reduction mechanism and the control board, thereby preventing lubricating oil, such as grease, applied to the speed reduction mechanism from scattering toward the control board.
Such an electric motor having a gear cover provided between a speed reduction mechanism and a control board is described in, for example, Japanese Patent Application Laid-Open Publication No. 2010-57299 (FIG. 3), and known as prior art. According to the electric motor described in Japanese Patent Application Laid-Open Publication No. 2010-57299 (FIG. 3), the gear cover is made from a steel plate by press working, etc., and a plurality of fitting claws integrally provided on the periphery of the gear cover are inserted in respective fitting holes of a resin gear case, so that the gear cover is fixed firmly to the gear case, and prevented from rattling.